The disclosure relates to turbine engines. More particularly, the disclosure relates to transport and storage of wired hoop structures.
FIG. 1 shows a gas turbine engine 20 having an engine case 22 surrounding a centerline or central longitudinal axis 500. An exemplary gas turbine engine is a turbofan engine having a fan section 24 including a fan 26 within a fan case 28. The exemplary engine includes an inlet 30 at an upstream end of the fan case receiving an inlet flow along an inlet flowpath 520. The fan 26 has one or more stages 32 of fan blades. Downstream of the fan blades, the flowpath 520 splits into an inboard portion 522 being a core flowpath and passing through a core of the engine and an outboard portion 524 being a bypass flowpath exiting an outlet 34 of the fan case.
The core flowpath 522 proceeds downstream to an engine outlet 36 through one or more compressor sections, a combustor, and one or more turbine sections. The exemplary engine has two axial compressor sections and two axial turbine sections, although other configurations are equally applicable. From upstream to downstream there is a low pressure compressor section (LPC) 40, a high pressure compressor section (HPC) 42, a combustor section 44, a high pressure turbine section (HPT) 46, and a low pressure turbine section (LPT) 48. Each of the LPC, HPC, HPT, and LPT comprises one or more stages of blades which may be interspersed with one or more stages of stator vanes.
In the exemplary engine, the blade stages of the LPC and LPT are part of a low pressure spool mounted for rotation about the axis 500. The exemplary low pressure spool includes a shaft (low pressure shaft) 50 which couples the blade stages of the LPT to those of the LPC and allows the LPT to drive rotation of the LPC. In the exemplary engine, the shaft 50 also drives the fan. In the exemplary implementation, the fan is driven via a transmission (not shown, e.g., a fan gear drive system such as an epicyclic transmission) to allow the fan to rotate at a lower speed than the low pressure shaft.
The exemplary engine further includes a high pressure shaft 52 mounted for rotation about the axis 500 and coupling the blade stages of the HPT to those of the HPC to allow the HPT to drive rotation of the HPC. In the combustor 44, fuel is introduced to compressed air from the HPC and combusted to produce a high pressure gas which, in turn, is expanded in the turbine sections to extract energy and drive rotation of the respective turbine sections and their associated compressor sections (to provide the compressed air to the combustor) and fan.
In an exemplary gas turbine engine, there may be a number of hoop structures to which sensors are mounted. One example involves sensors used to measure blade to case clearance. The hoop structure may form an outer air seal circumscribing a stage of blades.
FIG. 2 shows an exemplary hoop assembly 100 comprising a structural hoop member 102 having an inner diameter (ID) face 104 in close proximity to tips 106 of blades 108 of the associated blade stage. The exemplary ID face 104 bears a rub coating 110 for interfacing with the blades. The exemplary hoop bears a circumferential array of sensors 112. The exemplary sensors 112 are capacitive sensors used by a data acquisition system (not shown) to measure capacitance between the sensors and the passing blades so as to, in turn, determine radial clearance between the blade tips and the sensors (and thus the ID face 104). In the exemplary embodiment, each sensor 112 is mounted in an associated mounting aperture 114 of the structural hoop. The exemplary apertures 114 are radial through-apertures in an inner diameter (ID) band portion (band) 116 of the structural hoop whose inner diameter (ID) surface is the face 104. The band also has an outer diameter (OD) surface 117 and a first end 118 and a second end 119.
Various structural hoop cross-sectional geometries are possible. The exemplary structural hoop has a flange 120 protruding radially outward from an inboard junction 121 with the band. The exemplary flange 120 has a circumferential array of mounting holes 122 extending between first and second faces 123 and 124. The holes 122 may be used to mount to an adjacent flange of an adjacent hoop or other structure. In the particular exemplary structural hoop, there is an outer/outboard band portion (band) 130 extending axially from a junction 132 the outboard periphery 126 of the flange 120 to a junction 134 with the inboard periphery 142 of a second flange 140. The flange 140 has an outer/outboard periphery 144 and first and second opposite faces 146 and 148. In this embodiment, an array of holes 150 between the faces 146 and 148 of the second flange may be used to mount to an outer case support (not shown). Myriad other physical geometries of hoop are possible.
There may be one or more of several fragile features associated with the sensors 112. FIGS. 3 and 5 show the sensor elements 160 themselves. Second, FIG. 5 shows the sensor element held by a ceramic insulator 162 in a sensor body or housing 164 (schematically shown with internal wiring omitted). Opposite the sensor element 160, the housing carries a plug-like cap 166 which, in turn, carries wiring 168. FIG. 5A shows a braze 170 between the wiring (wire lead) 168 and an aperture 172 of the cap 166. The braze 170 and the wire lead 168 itself are potentially fragile. The exemplary wire lead 168 is a single wire extending off for length and formed in a loop for storage/transport. On installation into the associated engine, the wire lead may be extended and connected to the relevant wiring harness. Alternative configurations may involve multi-wire bundles and the like.